Lubricant



Patented July 6, 1943 LUBRICANT Elmer William Cook, New York, N. Y.,assignor to Tide Water Associated Oil Company, New York, N. Y., acorporation of Delaware No Drawing. Application November 16, 1940,

Serial No. 365,945

' 13 Claims.

This invention relates to lubricant compositions. More particularly, itis concerned with mineral oil lubricants adapted-to the lubrication ofbearing surfaces operating under high pressures.

The bearing surfaces of certain modern machines such as gear-teeth andth like are subjected to considerably higher pressures in use than wasthe case in the past, and it is now well known by those familiar withthe art that the ordinary mineral oil lubricants formerly used are noteffective for the lubrication of such bearing surfaces. In theautomotive field, for example, the employment of hypoid gears and theuse of higher powered engines in connection therewith has resulted ingreatly increased operating pressures at the bearing surfaces of suchgears, requiring improved lubricants for effective lubricationthereof.

It has been found that certain substances when added to minerallubricating oils greatly increase the load-carrying properties andresult in lubricant compositions capable of efiectively lubricatinggears and the like operating under extreme pressure conditions. Theseadditive substances usually contain either chlorine or sulfur, or both,and the compositions comprising lubricating oil and relatively minorproportions of such additives are known as extreme pressure lubricantsor hypoid lubricants.

A primary object of the present invention is to provide an improvedlubricant of the extreme pressure type capable of effectivelylubricating bearing surfaces operating under high pressures.

It is generally believed by those familiar with the art that theeffectiveness of extreme pressure lubricants is due to the formation ofa load-carrying film upon the bearing surfaces as a result of reactionwith the additive substance. The additive substance must. therefore, besufliciently reactive or unstable as toform such a protective film. Manyof the additives heretofore proposed, however. have been found to be tooreactive or unstable with the result that undesirable corrosive reactionproducts were produced which cause objectionable corrosion of the metalparts of the machines; This objectionable corrosive effect isparticularly noticeable when certain compounds containing chlorine areused as additives.

In accordance with the present invention I have discovered thatcompounds of the class of alkyl thioethers containing substitutedthiocarbonate groups have extremely high load-carrying capacities andproduce effective and satisfactory extreme pressure lubricantcompositions. More particularly, I have found that members of the classof sulfur-containing compounds known as dixanthyl dialkyl thioethers maybe incorporated in lubricating oils, particularly petroleum lubrieatingoilsto produce effective extreme pressure lubricants. The dixanthyldialkyl thioethers may be represented by the following structuralformula N I s in the compounds of this invention is believed largelyresponsible for the markedly high loadcarrying capacity of the lubricantcompositions I hereindescribed while the high oil-solubility andrelatively low corrosiveness of these agents may be attributed mainly tothe absence of active chlorine and the presence and arrangement of thexanthate and alkyl groups, and to the general structure of themolecules.

The'described class of thioethers may be prepared by reacting olefinswith sulfur monochloride to produce a dichloroalkyl thioether and thenreacting the latter with an alkali metal salt of an alkyl xanthate. Thefirst reaction is suitably carried out at to C. with the .oleflns inslight excess. Reaction of the chloroalkyl thioether with alkali metalalkyl xanthate is carried out by refluxing in alcoholic or methyl ethylketone solution, or the like.

The dichloroalkyl thioethers resulting from the reaction of olefins withsulfur monochloride are quite eflicient as extreme pressure agents, but

reactive chlorine which causes corrosion of metal containers and machineparts. By treatment with alkyl xanthate this active chlorine is rewhereR, R and R" are aikyl groups.

Of particular importance is the fact that relatively cheap and readilyavailable mixtures of olefins, such as cracked gasoline and the like,may be employed as starting materials, resulting in mixtures ofdixanthyl dialkyl thioethers which are relatively inexpensive and veryeffective as extreme pressure agents.

The dixanthyl dialkyl thioethers of this invention are adequatelysoluble in mineral oils, and the proportions of these additives to beused in my extreme pressure compositions may be varied over a wide rangeas desired. The additive substance is generally effective, however, inminor proportions. I have found that in practice the incorporation ofabout of the stated additive in petroleum lubricating oil compositionsprovides an extreme pressure lubricant which is suitable for lubricationof gears and the like operating under high pressure conditions.

As illustrative substances of the class which I have found to beparticularly effective extreme pressure agents according to thisinvention, the following are cited:

Di methyl xanthyl amyl) thioether Di( ethyl xanthyl amyl) thioether(resulting from reacting amylene-l and sulfur monochloride and treatingthe reaction product with potassium methyl xanthate and potassium ethylxanthate respectively) Diibutyl xanthyl limonyl) thioether (fromreacting dipentene with S2Cl2 and treating the reaction product withpotassium butyl xanthate) To show the load-carrying capacity of theextreme pressure agents of the type described herein a lubricantcomposition was prepared consisting of a distillate petroleumlubricating oil, de-.

rived from a Coastal crude, having an A. P. I. gravity of 23.7; flash(open cup) 375 F.; pour 20 F.: viscosity at 100 F. 203; color (A. S. T.M.) 2 /2: and carbon residue 0.03, and 10% of di- (methyl xanthyl amyl)thioether. Other lubricant compositions were also prepared consisting of90% of the lubricating oil described and 10% of di(ethyl xanthyl amyl)thioether, and di(butyl xanthyl limonyl thioether respectively. Thesethree lubricant compositions were then tested to determine their extremepressure characteristics on a standard testing machine known as the S.A. E. machine.

The S. A. E. machine test is recognized as a standard method fordetermining extreme pressure characteristics of lubricating oils. Thismachine, which is fully described and illustrated on page 296 of the S.A. E. Journal (Transactions),

vol. 39, No. 1, July 1936, is equipped with two special steel rings(Timken test cups) engaged at their outer surfaces in theoretical linecontact. Each of these rings is rotated at a different speed. The ringsare pressed together by means of a screw and lever system at a definiterate of loading, the load being indicated by a large scale dial. Thelubricant to be tested is placed in a container partially surroundingone of the rings, the lubricant being in contact with said ring, so thata film of lubricant is continuously supplied to the engaging surfaces ofthe rings by rotation of the rings. The criterion of the machine is theload at which the test rings start to scuff which is shown by linesappearing on the surfaces.

In the test the ratio of the speeds of rotation of the two rings was14.6 to 1, the speed of the fastest being 1000 R. P. M. The loading ratewas 83.5 lbs. per second.

Although the load was increased during the test until the upper limit ofthe dial reading (590 lbs.) had been reached there was no indication ofscufilng of the rings in the case of any of the three above-describedoil compositions. Samples of the mineral oil described above with noadditive substance failed in the test when the dial reading reachedabout 30 pounds.

This test clearly proves the compositions of this invention to be veryeffective extreme pressure lubricants and indicates their suitabilityfor use in hypoid lubricants and the like.

The invention, in addition to the improved lubricants disclosed herein,also includes methods of lubricating bearing surfaces of gears and thelike by application of said lubricants thereto.

I claim:

1. An extreme pressure lubricant composition comprising a lubricatingoil and a minor proportion of a dixanthyl dialkyl thioether.

2. An extreme pressure lubricant composition comprising a minerallubricating oilrand a minor proportion of a product obtained by,substituting active chlorine of a chloroalkyl thioether with athiocarbonate group.

3. An extreme pressure lubricant composition comprising a minerallubricating oil and a minor proportion of a non-chlorinated dixanthyldialkyl thioether.

4. An extreme pressure lubricant composition comprising a minerallubricating oil and a compound of the formula where R, R and R" arealkyl groups and 2:1 or 2, said compound being effective to impartextreme pressure lubricating characteristics to the composition.

5. An extreme pressure lubricant composition comprising a major portionof a mineral lubricating oil and a minor portion of dixanthyl dialkylthioether obtained by substituting the active chlorine of chlorodialkylthioethers derived from cracked gasoline olefins with alkyl xanthylgroups.

6. An extreme pressure lubricant composition comprising a major portionof a mineral lubricating oil and a minor portion of dixanthyl dialkylthioether obtained by substituting the active chlorine or chlorodialkylthioethers derived from olefin mixtures with alkyl xanthyl groups.

7. An extreme pressure lubricant composition comprising a lubricatingoil and about 10 per cent of a dixanthyl dialkyl thioether.

8. An extreme pressur lubricant comprising a major portion of a minerallubricating oil and a minor portion-of di(methy1 xanthyl amyl)thioether.

9. An extreme pressure lubricant comprising a major portion of a minerallubricating oil and a minor portion of di(ethyl xanthyl amyl) thioether.

10. An extreme pressure lubricant comprising a major portion of amineral lubricating oil and a minor portion of di(butyl xanthyl limonyl)thioether.

11. An extreme pressure lubricant comprising a major portion of amineral lubricating oil and a minor portion of a substance produced byreact ing an olefinic material with sulfur chloride to producedichloroalkyl thioether and substituting chlorine groups of thedichloroalkyl thioether with xanthyl groups.

12. Method of lubricating bearing surfaces which are subjected to highpressures which comprises applying to said surfaces a lubricantcomposition comprising lubricating oil and a dixanthyl dialkyl thioethereffective to give to said composition extreme pressure characteristics.

13. An extreme pressure lubricant composition comprising a minerallubricating oil and a product obtained by substituting active chlorineof a chloroalkyl thioether with xanthyl radicals.

' ELMER WILLIAM COOK.

